North Korean dictator Kim Jung Un boldly claimed Thursday that his country had developed a hydrogen bomb, a ferocious weapon that would mark a major advancement in North Korea’s nuclear weapons development.

But hold on a minute. A hydrogen bomb is more than just a really big nuke, and is not a trivial thing to build. It would almost certainly require testing, which the U.S. would likely have detected, as well as technical sophistication and resources that it’s not clear North Korea possesses.

That’s the good news. However, nuclear weapons experts told The Daily Beast, it’s possible that North Korea may have found some way to enhance the nuclear weapons it already has. That effort could result in more powerful bombs, although nothing close to the city-wasting powers of the dreaded “H-bomb.”

It’s possible that North Korea could use certain materials “to boost the yield of a nuclear weapon,” said Jeffrey Lewis, the director of the East Asia Nonproliferation Program at the James Martin Center for Nonproliferation Studies at the Monterey Institute of International Studies. Lewis pointed to deuterium, a hydrogen isotope, or lithium-6, a key isotope in nuclear physics, as items that could make Pyongyang’s weapons more potent.

“China did this with its third [nuclear] test and other states, like South Africa and Israel, moved in this direction with little or no testing,” Lewis said.

David Albright, a physicist and the founder and president of the Institute for Science and International Security, also said North Korea was unlikely to have built a true hydrogen bomb, which is exponentially more powerful than the weapons it’s known to have. But it may have tried to boost the yield of its current weapons.

“My own view is that they’ve been working on it,” Albright said, noting that North Korean officials have alluded to work on certain materials that would be key to boosting the explosive yield beyond what they seem to have mastered now, on the order of 5 to 10 kilotons. (The bomb that the U.S. dropped on Hiroshima in 1945 yielded about 15 kilotons.)

One way to boost the yield is through the development of thermonuclear weapons, which work in two stages: a fission reaction sets off a secondary reaction, producing a much bigger explosion. The hydrogen bomb is a thermonuclear weapon.

But there are ways to use thermonuclear material to boost the yield of weapons that only use one stage. That’s what South Africa did, boosting the yield from 15 kilotons to 100 kilotons, Albright said.

“I don’t even think they’re there yet,” Albright said of the North Koreans. “They would have tested something at a much higher yield.” And, he noted, even a weapon with a yield of hundreds of kilotons is a far cry from the true hydrogen bombs that the U.S. and Russia have built, which have yields of thousands of kilotons.

Just how advanced North Korea’s plan is has been a subject of debate. In April, the country repeated earlier claims that it had miniaturized a weapon, that is, created a warhead that could be placed atop a missile. But U.S. officials and experts at the time cast doubt on that. Also, North Korea has a long history of exaggerating its military capabilities and of saber rattling.

But none of the experts The Daily Beast consulted was ready to dismiss as pure fancy the idea that North Korea has expanded its nuclear power.

“Let’s remember the Kim regime eventually possesses every weapon it boasts of, maybe not at the time of the claim, but eventually,” said Gordon Chang, the author of Nuclear Showdown: North Korea Takes On the World and a Daily Beast contributor. “The regime has the capability of surprising us, and they do that every so often. For one thing, we always forget they have help from their Chinese and Russian friends and their Iranian bankers.”

Albright, too, noted that the North Koreans could have obtained technical assistance from Russian experts. And, he said, there is enough unclassified research out there that North Korea may have figured out how to boost its yields without conducting tests.

And of course, even if North Korea hasn’t obtained the sophisticated weapon that Kim claimed this week, it’s probably trying.